In the operation of turbomachinery such as gas turbine engines, there are requirements to inhibit air or gas flow between certain portions of the engine. For example, in an axial flow gas turbine engine, it is desirable to inhibit flow between stages of the compressor and of the turbine such as by interstage leakage across the tips of blading members. In addition, portions of the compressor section and of the turbine section are isolated above rotating shafts and drums through the use of abradable labyrinth-type seals, one element of which can be a porous or a honeycomb-type structure, for example cooperating with at least one opposed tooth member. Frequently such a honeycomb structure is filled with a porous abradable material which is abraded away upon contact with an opposing member when there is relative rotation between such components. One type of such a seal member is described in U.S. Pat. No. 3,916,054--Long et al, issued Oct. 28, 1975, the disclosure of which is incorporated herein by reference.
Although there has been a variety of such seal members identified, gas turbine engine experience has shown that a smooth, substantially continuous surface decreases air turbulence which might otherwise be generated through use of an open cell honeycomb or labyrinth-type member such as is described in the above-incorporated and other prior art patents. As a result of such air turbulence, temperature increases have been observed across such a seal. Such increased temperature can affect the mechanical properties of components downstream of the seal.